How Many Calories Do I Need?

By Sanae Tanaka, M.D.

Many people who have had weight loss surgery wonder how many calories (kcal) they need each day to reach and maintain a healthy weight. If you are not far out post-WLS, your calorie intake will be minimal, and will be below your intake for weight maintenance. In those first few months after surgery, it is critical that you stick to the recommendations from your doctor and dietitian.

However, for reference, the basic recommendation for calories when trying to lose weight (without WLS) is that you take in 500-1000 calories less than your daily caloric requirement, as calculated from your present weight and activity level. The minimum recommended calories while on a diet are 1,000-1,200 kcal/day for women, and 1,200-1,600 kcal/day for men. Most of the popular diets aim for 1,500 kcal/day.

General Physical Requirements

Your basic caloric needs are determined by your weight and how active you are. Your ideal weight range depends on your height, and equates to a Body Mass Index (BMI) of 18.5-24.9 (median 22). But, in addition to your weight, you also have to consider how many calories you burn doing daily activities to determine how many calories you need to take in. Unless you are math savvy, you will need a calculator to figure it out. However, here’s a simple equation that will give you the general range by showing you how many calories you burn daily for each pound you weigh and your level of activity.

• Sedentary, seated during most of the day: 11-13.6 kcal/lb/day
• Moderate labor, on your feet most of the time: 13.6-16 kcal/lb/day
• Heavy labor, competitive or professional athlete: 16+ kcal/lb/day

The upper limit for heavy labor is not set because it is is variable, depending on the amount of activity. For example, an average heavy laborer uses anywhere from 3000 to 4500 kcal/day, depending on stature, while for very competitive professional athletes, it may go up to over 6000 kcal/day.

Another important note: Although they are on their feet much of the day, homemakers generally fall into the “sedentary” category. This is because the muscular distribution of women differs from men, so the expenditure level is lower for women. An inactive homemaker should use the lower end of the scale, and a very active housewife, the higher end. So, unless you are doing some pretty heavy housework daily for hours, go by the sedentary and not the moderate labor figures to calculate your daily caloric needs.

Example Calculation

The examples below are for someone who works at a desk job and is mostly inactive. For each scenario, the total represents the daily caloric requirement to maintain the individual’s current body weight. (Note: This does not mean that you should maintain this body weight, only the amount of calories it takes to stay at that level.)

• 5′5”, 300lb (BMI 49.9): 300 x 11-13.6 = 3300-4080 kcal.
• 5′5”, 150lb (BMI 24.96): 150 x 11-13.6 = 1650-2040 kcal.
• 5′5”, 130lb (BMI 21.5): 130 x 11-13.6 = 1430-1770 kcal.

Distributing the Calories

Of the foods that you eat, carbohydrates, proteins and fat are the major nutrients, called macronutrients, and the source of the calories you burn. The recommended dietary calorie distribution is:

• Carbohydrates: 45-60% (No less than 130g because of the brain/central nervous system requirements)
• Protein: 10-35% (At least 0.36g/lb/day)
• Fat: 20-30%

Calculating the Actual Amount of Each Macronutrient

To calculate how much you can eat in terms of volume of food, you have to convert the calories into grams. (After all, you can’t “weigh” the calories, they are a unit of energy.)

• Carbohydrates: 1g = 4 kcal
• Protein: 1g = 4 kcal
• Fat: 1g = 9 kcal

So, as an example, let’s look at a 1600 calorie diet, with the following distribution:

• Carbohydrates 50% = 800 kcal = 200g
• Protein 30% = 480 kcal = 120g
• Fat 20% = 320 kcal = 35.5g

An important point to note when going food shopping or planning your meal is that there are no “pure” foods that contain nothing but a single nutrient, unless it has been processed and refined, as in refined sugar. Just about every natural food contains multiple nutrients, so you have to choose the food by its major content. For example, rice—which is a major carbohydrate food—contains 77% carbohydrates, but also 6% protein, and 1% fat. With beef, depending on which portion, the counts are around 20% protein, anywhere from 5%-30% fat, and negligible carbohydrates.

Maintenance Mode

First things first, you need to ask your doctor/dietitian what your maintenance intake should be, and what the macronutrient balance should be. If you need to figure out by yourself how many calories you need, the most important point is that daily intake must equal your daily expenditure. If you eat more than you need, your body will stock up the extra. If you eat less than you need, you will keep on losing. Keeping that in mind, you will have a general idea of how much you can eat, and how to balance your food intake when you reach goal. If you make the right choices with your food, you may find that you can eat a fair amount (though not as much as when your weight was at its maximum) while keeping the calories low.

Calculating your daily caloric intake immediately after gastric bypass surgery and for long-term maintenance can seem confusing. But with practice, running the numbers will become second nature, and you will also be more familiar with the calorie count and nutritional values of your favorite foods. Remember to take one day at a time as you learn healthy eating habits post-WLS. May your journey be full of rewards for all your hard work.